Despite much progress in terahertz (THz) technology, existing THz modulators have not yet offered the modulation specifications oftentimes required for high-performance THz imaging, spectroscopy, and communication systems. More specifically, there is a lack of high-performance THz modulators offering large modulation depths over a broad range of THz frequencies.
Modulation schemes and techniques in the visible and infrared regime—such as, for example, those based on carrier injection/depilation in solid-state devices, Mach-Zehnder interferometers, Fabry-Perot filters, liquid crystals, magneto-optic effects, deformable mirrors, and beam deflectors—can have difficulty meeting high-performance modulation specifications at THz frequencies due to the lack of materials with the desired properties at THz frequencies, as well as the practical challenges associated with scaling device dimensions to operate efficiently in the THz regime. Thus, existing modulation schemes and techniques typically offer a tradeoff in terms of modulation depth, modulation bandwidth, modulation speed, modulation voltage, signal attenuation, or some combination thereof, when adapted for operation in the THz regime.
Other modulation schemes and techniques involve the use of metamaterials, which have a spectral response that can be engineered by their geometry, rather than being limited by the characteristics of natural materials at THz frequencies. However, the modulation bandwidth of the demonstrated metamaterial-based terahertz modulators have been somewhat limited by the resonant nature of the device configurations being employed.